FIG. 1 depicts a schematic diagram of wireless local-area network (LAN) 100 in the prior art comprising access point 101, stations 102-1 through 102-K, wherein K is a positive integer, and shared-communications channel 103. Stations 102-1 through 102-K are typically associated with host computers (not shown), such as notebook computers, personal digital assistants (PDA), tablet PCs, etc. Stations 102-1 through 102-K enable communications between (i) the host computers or (ii) the host computers and other devices, such as printer servers, email servers, file servers, etc. Access point 101 enables stations 102-1 through 102-K to (i) coordinate transmissions between each other and (ii) communicate with devices in other communications networks.
Access point 101 and stations 102-k, for k=1 through K, transmit data blocks called “frames” over shared-communications channel 103. If two or more stations (or access point 101 and a station) transmit frames simultaneously, then one or more frames can become corrupted, resulting in what is called a “collision”. Local-area networks, therefore, typically employ a medium access control (MAC) protocol for ensuring that a station can gain exclusive access to shared-communications channel 103 for an interval of time in order to transmit one or more frames. A “protocol” is a set of communications procedures that relate to the format and timing of transmissions between different stations.
In wireless local-area networks that are based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, the medium access control protocol is based on a mechanism called “carrier sense multiple access” (CSMA), in which station 102-k or access point 101 can detect whether shared-communications channel 103 is busy or idle. If shared-communications channel 103 is busy, station 102-k or access point 101 will wait until the channel is idle before attempting to transmit a signal that conveys a message.
Shared-communications channel 103 can be used by stations that operate in accordance with different protocols. For example, the IEEE 802.11 standard (e.g., 802.11a, 802.11b, 802.11e, 802.11g, etc.) describes one set of protocols, and the Bluetooth standard describes another set of protocols. A particular station (e.g., station 102-1, etc.) might handle an IEEE 802.11 protocol or a Bluetooth protocol, or both. A station that is capable of handling multiple protocols (i.e., a “multi-protocol station”) comprises multiple protocol subsystems, or “parts”, in which each part handles communications in accordance with a specific protocol.
Coordination of the IEEE 802.11 and Bluetooth protocols in a multi-protocol station can become particularly difficult when the Bluetooth part transmits or receives packets that are synchronous connection oriented (SCO) (e.g., voice packets, etc.), because such packets are often repeatedly transmitted at high data rates. As a result, Bluetooth coexistence mechanisms, such as the IEEE 802.15.2 set of standards, have been introduced in the prior art to address this problem. Such coexistence mechanisms coordinate a multi-protocol station's transmission of (i) Bluetooth synchronous connection oriented voice packets, and (ii) frames of another protocol. These mechanisms, however, do not prevent collisions that can occur when access point 101 transmits an IEEE 802.11 frame at the same time that a multi-protocol station transmits a Bluetooth packet.
Another approach in the prior art is to use the IEEE 802.11 Power Save state to cause access point 101 to queue outbound IEEE 802.11 traffic that is intended for station 102-k. The queuing occurs during the time that station 102-k indicates that it is inactive in the IEEE 802.11 sense as far as access point 101 is aware, but actually remains active in the Bluetooth sense. The technique of entering and exiting power save mode to allow time for Bluetooth operation, however, does not effectively support synchronous connection oriented operation of Bluetooth for some applications (e.g., voice, etc.). The repetition rate of synchronous connection oriented Bluetooth is so rapid that it is often impractical to rely on the IEEE 802.11 frames that indicate the rapid changes in power save state.
Therefore, a need exists for an improvement in how stations that operate in accordance with different protocols coexist with an access point without some of the costs and disadvantages in the prior art.